2.7 SPECTRA

Question 1

Irradiance of light

Answer 1

I=P/A where A area in m2

Question 2

Irradiance of laser light

Answer 2

light from laser is monochromatic, coherent, forms a parallel beam

Question 3

why does irradiance matter?

Answer 3

to understand the activity of the Sun and climate and to research the impact of solar activity on the Earth’s climate

Question 4

How to improve the quality of the experiment of investigating irradiance?

Answer 4

1. Darken the room. Place the light a distance from lamp
2. Mearsure the distance between the objects
3. Repeat these measurements for different distances

Question 5

the graph of average irradiancde

Answer 5

against 1/d2 is a straight line
hence I1d1(squared)=a constant

I1d12=I2d22

Question 6

A point source is one

Answer 6

which irradiates equally in all directions, which is a sphere
hence A=4pir2

ex; Sun or lamp

Question 7

A laser is not a point source

Answer 7

and its irradiance doesn’t follow the inverse square law

Question 8

An emission spectrum is

Answer 8

the range of colours given out/ emitted by a light source

Question 9

Kinds of emission spectra

Answer 9

1. Continious
2. Line

Question 10

Continuous spectrum

Answer 10

produced when white light is passed through a grating or prism
All frequencies of radiation (colours) are present

Question 11

Line Spectrum

Answer 11

produced by light from a star or an electrical discharge lamp containing vapour of elements (пари елементів) such as sodium or mercucy
Consist of bright lines which are produced by electrons making transition from a higher energy level to lower
The** number of lines** in the spectrum corresponds to the number of possible transitions

Question 12

An instrument which spreads light out into its wavelengths, creating a spectrum

Answer 12

spectroscope and spectrometer

Question 13

Bohr Model of the Atom

Answer 13

A model of the atom which describes the arrangement of electrons (розташування) within it.

It proposes that electrons are in circular orbits around the nucleus which correspond to the energy level

The electrons can only occupy discrete energy levels, ground state or an excited state

Question 14

energy level diagram

Answer 14

a diagram used to study the movement of electrons between energy levels in the atom

Question 15

Ground state Eo

Answer 15

the lowest energy orbit

Question 16

Excited state

Answer 16

an energy level above the ground state
electrons can move into it when they gain energy

Question 17

Ionisation level is

Answer 17

the highest energy level

where E=0

Question 18

all excited states

Answer 18

have negative energy level

Question 19

Electron transition is

Answer 19

the movement of an electron from one energy level to another

Question 20

ENERGY LEVEL (falling electron)

Answer 20

E2- E1=differenceE=hf

Question 21

when the electron drops the energy is released

Answer 21

in the form of a** photon** where its energy and frequency are related by the energy difference btween two levels

Question 22

atomic fingerprint

Answer 22

is a spectra of the element

Question 23

how bright line is depends on

Answer 23

the number of photons emitted

Question 24

to be excited the electron should be

Answer 24

heated (discharged tubes)
high voltage (filament lamps)
nuclear fusion (stars)

Question 25

wavelength of red and violet

Answer 25

red 400nm
violet 700nm

Question 26

in the continiuous spectrum the electrons

Answer 26

are not free, are shared between atoms resulting in a large numer of possible energy levels

Question 27

PHOTON EMISSION

Answer 27

occurs when an electron drops from a higher energy level to a lower energy level
only photons with energies exactly matched to the difference between two energy levels can be emittedВипромінюється

Question 28

Photon Absorption

Answer 28

an electron will move to the** higher** energy level when it absorbs the energy of a photon
Only photons with same matching energies can be absorbed(Поглинається)

Question 29

Absorption Spectrum

Answer 29

produced when light with countinious spectrum passes through a low-pressure gas
they appear as black lines on countinuous spectrum

FORMULAR; E2=E1+hv (frequency)

Question 30

Frauhofer lines

Answer 30

absorption lines in the spectum of the **sunlight **
they provide evidence for the composition of the Sun’s outer (зовнішній) atmosphere